This invention relates to storage area management of automatically expandable storage system volumes in a computer system that uses a computer and a storage system.
In a common computer system that uses a computer and a storage system, the computer stores data in a storage area provided by the storage system. When the computer has more data to store, the capacity of the storage area (hereinafter also referred to as volume) needs to be expanded.
One way to expand a volume is stopping the operation of the computer system temporarily and, after the volume is expanded, allowing the computer system to resume the use of the volume. A drawback of this volume expansion method is that it halts the business operation. JP 2003-15915 A overcomes the drawback by automatically expanding the actual capacity of a storage system volume enough to compensate a capacity shortage caused by data write to the volume, without changing the computer-recognized volume capacity.
A volume that can be managed without changing the computer-recognized volume capacity may be referred to as a virtual volume in the following description. An area including physical storage area that is used to expand volume capacity to compensate a capacity shortage caused by data write to the volume may hereinafter be referred to as a virtual pool. A volume registered to a virtual pool may hereinafter be referred to as a virtual pool volume. An area allocated in order to expand the capacity enough to accommodate data write to a virtual volume may hereinafter be referred to as an allocated area.
JP 2007-257317 A discloses a technique of removing the above-mentioned allocated area of a virtual volume. With this technique, a file server and a storage system share information on the state of each area that meets the above-mentioned definition of an allocated area, and the file server removes an allocated area that is not in use.